tapering tubes?

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pezman
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tapering tubes?

Post by pezman » Sun Oct 17, 2004 2:59 am

I want to start fiddling with the creation of a "Bruno-O" high compression pulsejet. The only uflow models that show promise consists tapered tubes end to end. Anyone got ideas on how to make a tapered tube (1" id -> 0.5" id) about a half meter long?

I think that the engine will take some fiddling to get is to work, so I'm hoping for a really simple technique. Careful "squashing" of the tube was the only idea that I've had so far.

steve
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Re: tapering tubes?

Post by steve » Sun Oct 17, 2004 3:22 am

how would you make one? a hammer, an anvil, and lots of patience

sounds like the tailpipe on the K-PT01b I built

http://www.pulse-jets.com/phpbb2/files/dsc01134.jpg
http://www.pulse-jets.com/phpbb2/files/dsc01041.jpg
http://www.pulse-jets.com/phpbb2/files/ ... nd_new.jpg
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larry cottrill
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Re: tapering tubes?

Post by larry cottrill » Sun Oct 17, 2004 3:25 am

I think the best idea I ever saw posted on something like that was from somebody [probably Mark] who suggested visiting junk shops to find tapered tubular steel table legs. Of course, those will be almost a metre long, but you might readily find one that you can cut the proper piece out of. It depends, of course, on whether you feel you need precise dimensions or just something reasonably close. They will almost certainly be plated or painted, but I've never found that to be particularly troublesome when working with steel pieces.

If you live in or near a good-size city, just set aside a Saturday to go tour the shops - you probably already know where some of them are.

L Cottrill

pezman
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Re: tapering tubes?

Post by pezman » Sun Oct 17, 2004 5:51 am

The table thing is sheer genius. The dimensions just need to be close enough for govt. work -- if the design is too sensitive to geometry, then it probably won't throttle, won't operate when its too hot or cold etc., etc.

I'll grab a table for long sections and maybe a chair for some shorter sections. If I can get a prototype running then I can go back and build it properly.

If a working engine ends up looking anything like the model, then I've noticed that tapered light poles seem to be just about the right dimension for a big engine ;). The pulses would be two 40 Hz waves (out of phase) with lots of harmonics -- one way to make the local papers, probably.

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Re: tapering tubes?

Post by Mark » Sun Oct 17, 2004 7:22 pm

I thought it was some likeable British fellow, I can't remember who suggested or posted a picture of some table legs. I suggested some tall flared stainless steel lamps I saw in a large hardware store in the lighting section that had ceiling fans, tall and short lamps, etc.

Mark

Hank
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Re: tapering tubes?

Post by Hank » Thu Oct 21, 2004 12:45 am

[quote="steve"]how would you make one? a hammer, an anvil, and lots of patience

To which I might add a template and a clear vision in your mind of where you want to wind up as far as form.
You might want to research the processes involved in forming.
Hank

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Re: tapering tubes?

Post by Bruno Ogorelec » Thu Oct 21, 2004 9:16 am

steve wrote:how would you make one? a hammer, an anvil, and lots of patience
I'd add the instruction a friend of mine said he had seen in the manual for a Japanese bike that arrived in kit form and had to be put together by the buyer:

"The building of this bicycle should be attempted only in the state of complete emotional balance."

Mike Everman
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Re: tapering tubes?

Post by Mike Everman » Thu Oct 21, 2004 11:41 am

LOL! As well as the running of it.
Mike Often wrong, never unsure.
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Mark
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Re: tapering tubes?

Post by Mark » Thu Oct 21, 2004 1:30 pm

I love those Chinese instructions too. I got them with my two lathes, and other things I have ordered. The writing is flowery and as if a child were trying to caution you ever so gently about a serious potential hazard should you botch the assembly and/or use the device after having one too many beers.
Something like "do not enjoy beer while lathe is spinning." It's a riot to read the well-intentioned but laughable warnings, the incongruity. Maybe something like this too, "electricity can be about, do not think of something else if wiring is suspected, memory in a capacitor may last ."
I should get out my manuals again.
Mark

Mike Kirney
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Re: tapering tubes?

Post by Mike Kirney » Thu Oct 21, 2004 1:58 pm

Most tables are about 30" or 32" high, so the legs would be slightly shorter than that.
Trig IS fun.

Bruno Ogorelec
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Re: tapering tubes?

Post by Bruno Ogorelec » Sat Oct 23, 2004 10:14 am

Mark wrote:I love those Chinese instructions too. I got them with my two lathes, and other things I have ordered. The writing is flowery and as if a child were trying to caution you ever so gently about a serious potential hazard should you botch the assembly and/or use the device after having one too many beers.
Something like "do not enjoy beer while lathe is spinning." It's a riot to read the well-intentioned but laughable warnings, the incongruity. Maybe something like this too, "electricity can be about, do not think of something else if wiring is suspected, memory in a capacitor may last ."
I should get out my manuals again.
Mark
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pezman
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Re: tapering tubes?

Post by pezman » Sat Oct 23, 2004 4:10 pm

lol

I'm glad I asked the question - not only got an answer, but the thread has taken such an interesting turn

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